Dopamine (3,4-dihydroxyphenylethylamine) is a biological molecule having a variety of actions, and mainly functions as a neurotransmitter in the central nervous system. In the body, dopamine is intracellularly biosynthesized by the action of two enzymes of tyrosine hydroxylase and DOPA decarboxylase with amino acid tyrosine as the origin.
Dopaminergic neuron is a neuron that synthesizes and releases dopamine as a neurotransmitter. In the brain, it is mainly present in the midbrain, and partly in the hypothalamus. Dopaminergic neuron present in the midbrain plays an important role in motility and emotional control. When midbrain dopaminergic neuron is degenerated or drops out, for example, severe neurodegenerative diseases such as Parkinson's disease and the like can be induced. One of the therapeutic approaches most expected to treat such neurodegenerative disease is a cell transplantation therapy including transplantation of a dopaminergic neuron to the target.
As a method for obtaining a dopaminergic neuron, a method including differentiating stem cells such as embryonic stem cell (sometimes to be referred to as ES cell in the present specification), induced pluripotent stem cell (sometimes to be referred to as iPS cell in the present specification) and the like into neuroectoderm, and further inducing differentiation into dopaminergic neuron is known at present.
Recently, it has been reported that a midbrain dopaminergic neuron is produced from floor plate cells. In addition, there have successively been reported a method including differentiating stem cells into floor plate cells by using two kinds of SMAD (Small Mothers Against Decapentaplegic) signaling inhibitors to obtain a midbrain dopaminergic neuron (patent document 1, non-patent document 1), a method for inducing a midbrain dopaminergic neuron by inducting floor plate cells from human stem cells and culturing the floor plate cells together with a neurotrophic factor (patent document 2, non-patent documents 2-4), and a method for efficiently inducing floor plate cells by reacting human ES cells with a GSK3 beta inhibitor and an activin/Nodal inhibitor (non-patent document 5).
However, the production efficiency of the dopaminergic neurons obtained by these methods remains low, and also, the cells are functionally insufficient since they cannot reproduce, in vitro, the responsiveness to oxidative stress and drug stimulation, and the like. Therefore, the development of a method for efficiently obtaining a high-quality dopaminergic neuron is still desired.